Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C303/00—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides
  • C07C303/02—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of sulfonic acids or halides thereof
  • C07C303/16—Preparation of esters or amides of sulfuric acids; Preparation of sulfonic acids or of their esters, halides, anhydrides or amides of sulfonic acids or halides thereof by oxidation of thiols, sulfides, hydropolysulfides, or polysulfides with formation of sulfo or halosulfonyl groups

Definitions

• the invention relates to a process for the preparation of alkanesulfonic acids.
• Alkanesulfonic acids are used in a number of technical applications. Long chain alkanesulfonic acids have e.g. Surfactant properties, while short chain ones such as methanesulfonic acid e.g. can be used as auxiliary chemicals for the electrodeposition of base metals such as tin or lead in the tinning of printed circuit boards for electronics or in the production of tinplate.
• alkyl mercaptans or diaikyl disulfides serve as starting materials, which are usually produced by the reaction of hydrogen sulfide with alcohols.
• the oxidation reaction of the alkyl mercaptans or the diaikyl disulfides to the corresponding alkanesulfonic acid can be achieved by various oxidizing agents. Hydrogen peroxide, chlorine, dimethyl sulfoxide or mixtures of dimethyl sulfoxide and hydroiodic acid and the electrochemical oxidation can be used as the oxidizing agent.
• WO 98/34914 describes an oxidation of mercaptans and / or dialkyl disulfides with Br 2 to alkanesulfonic acids.
• the Br is preferably obtained from HBr for easier handling.
• the oxidation of HBr to Br can be carried out with oxygen in the presence of catalytic amounts of nitric acid or with Nitric acid itself as an oxidizing agent.
• the nitrogen oxides formed during the oxidation of HBr with nitric acid are reoxidized to nitric acid with oxygen.
• the oxidation of HBr to Br 2 and the oxidation of the mercaptans and / or diaikyl disulfides with Br 2 can be carried out in separate reactors.
• Another way of producing the alkanesulfonic acids is to oxidize the alkyl mercaptans or diaikyl disulfides with oxygen in the presence of nitrogen oxides or nitric acid. Oxidation with oxygen in the presence of nitric acid is e.g. in US 2,697,722 and US 2,727,920.
• alkyl mercaptans or polysulfides such as dialkyl disulfides
• the alkyl mercaptan or the polysulfide is gradually oxidized to the desired alkanesulfonic acid.
• Mixtures of nitrogen monoxide, nitrogen dioxide and nitrous oxide are formed during the oxidation.
• the nitrogen monoxide and the nitrogen dioxide are converted into pure nitrogen dioxide or nitric acid by the oxygen absorbed in the nitric acid, which are again available for the formation of alkanesulfonic acids.
• the nitrous oxide is discharged.
• a disadvantage in this process is the high proportion of laughing gas formed, which, as so-called “greenhouse gas", similar to halogenated methanes and ethanes, leads to ecological problems and therefore has to be separated from the exhaust gas stream in a technical system. Furthermore, the exhaust gases also contain larger amounts Amounts of nitrogen and sulfur compounds that also have to be removed at great expense.
• reaction temperatures in these reactions are usually in the range between 25 and 70 ° C. At these temperatures, however, none Full conversion to alkanesulfonic acid reached. For example, in the conversion to methanesulfonic acid, the reaction under these reaction conditions partly remains at the level of the intermediate methanethiosulfonic acid S-methyl ester.
• This intermediate product is an unstable compound that splits off sulfur dioxide from 90 ° C and decomposes spontaneously and strongly exothermically at 170 ° C.
• the object is therefore to provide an economically attractive process which enables the preparation of alkanesulfonic acids in high purity and in good yields and which almost completely suppresses the formation of nitrous oxide.
• This object is achieved by a process for the preparation of alkanesulfonic acids, comprising the following steps: (a) oxidation of alkyl mercaptans and / or dialkyl disulfides and / or dialkyl polysulfides with three to nine sulfur atoms with nitric acid with formation of alkanesulfonic acids, water, nitrogen oxides and further by-products,
• step (b) Regeneration of the nitrogen oxides obtained from step (a) with oxygen to nitric acid and recycling of the nitric acid in step (a).
• steps (a) and (b) are carried out in separate reaction spaces.
• step (a) An oxidation of the alkyl mercaptan or of the dialkyl disulfide with (atmospheric) oxygen is accordingly carried out as a gross reaction.
• the nitrogen oxides formed in step (a) are low-oxidized nitrogen compounds (NO / NO 2 mixtures) which are reoxidized in step (b) to pure or nitric acid-containing nitric acid.
• the nitric acid used in the process according to the invention can accordingly be pure or nitric acid containing nitrogen dioxide.
• step (a) The spatial separation of the oxidation of mercaptans and / or dialkyl disulfides and / or dialkyl polysulfides with three to nine sulfur atoms to alkanesulfonic acid (step (a)) and the regeneration of the nitrogen oxides (step (b)) is advantageous because both reaction steps, step (a ) and step (b), can be carried out separately from one another under optimal reaction conditions. As a result, the formation of nitrous oxide can be almost completely suppressed and very good yields of alkanesulfonic acids can be achieved.
• the method according to the invention is preferably carried out continuously.
• step (a) is carried out at reaction temperatures from 50 ° C. to 150 ° C., preferably from 100 ° C. to 140 ° C.
• the working pressure in step (a) is generally between 100 mbar and 8 bar, preferably at normal pressure.
• the mercaptans and / or diaikyl disulfides and / or dialkyl polysulfides used in the process according to the invention contain carbon residues which can be aliphatic or cycloaliphatic.
• the hydrocarbon radicals are particularly preferably linear or branched aliphatic hydrocarbon radicals. These preferably contain 1 to 20, particularly preferably 1 to 14 carbon atoms.
• the residues are very particularly preferably methyl residues and thus the alkyl mercaptans or dialkyl disulfides are methyl mercaptan or dimethyl disulfide.
• Diaikyl disulfides are preferably used in the process according to the invention.
• the diaikyl disulfides are usually made from hydrogen sulfide and methanol, although other access routes are known in the literature.
• the diaikyl disulfides are particularly preferably prepared by oxidation of alkyl mercaptans with sulfur dissolved in an organic dialkyl disulfide using an amine as a catalyst.
• the alkyl mercaptans can be used as a “crude mercaptan stream”, that is to say as a mercaptan stream not purified by extraction or distillation, from the reaction of alcohols with hydrogen sulfide over a suitable catalyst.
• dialkyl disulfide is a storage-stable feed material and is therefore safe to handle.
• This process is described in the simultaneously filed patent application No. 198 54 427.8 (official file number) with the title "Process for the preparation of dialkyl disulfides".
• the preferred dialkyl disulfide is converted to alkanesulfonic acid and must therefore be replenished.
• the subsequent metering of dialkyl disulfides can be carried out in the vapor phase of the reaction mixture in step (a) or immersed under the liquid surface of the reaction mixture.
• the diaikyl disulfides When added to the vapor phase of the reaction mixture, intimate mixtures of dialkyl disulfides and nitrogen oxides can be formed which are explosive. For this reason, the diaikyl disulfides are preferably metered into the reaction mixture, immersed in the liquid surface.
• the immersion can take place, for example, in the reactor via an immersion tube or in a circulating circuit via a mixing nozzle.
• the molar ratio of alkyl mercaptans and / or dialkyl disulfides and / or dialkyl polysulfides with three to nine sulfur atoms to nitric acid is generally 1: 1 to 1:10, preferably 1: 2 to 1: 6, particularly preferably 1: 2 to 1: 4th
• the molar ratio is generally 1: 2 to 1:20, preferably 1: 3 to 1:10, particularly preferably 1: 3 to 1: 6.
• dialkyl polysulfides are preferably used in a mixture with mercaptans or dialkyl disulfides.
• the oxidation can take place in a reactor or in a reactor cascade with a high degree of backmixing, e.g. in a stirred tank or loop reactor, or in a low backmixing reactor, e.g. in one
• step (a) is in one
• Reactor or carried out in a reactor cascade with a high degree of backmixing If reactors or reactor cascades with a high degree of backmixing are used, these can optionally be below the
• Boiling temperature of the reaction mixture are operated as pure oxidation reactors or at the boiling temperature of the reaction mixture, whereby a concentration of the reaction mixture can already be achieved during the synthesis by separating off dilute aqueous nitric acid present in excess.
• the oxidation part of the plant consists of a reactor cascade of two reactors with a high degree of backmixing, for example two stirred tanks.
• the temperature in the first reactor, into which alkyl mercaptan or dialkyl disulfide or dialkyl polysulfide and nitric acid are metered, is preferably between 50 and 140 ° C., particularly preferably between 80 and 120 ° C.
• the second reactor which is charged with the overflow of the first reactor, is preferably operated between 100 and 150 ° C., particularly preferably between 130 and 150 ° C. while the contents of the vessel are evaporated.
• the residence times of the reaction mixture in both reactors can be between 10 minutes and 10 hours, preferably between 1 and 3 hours.
• Part of the heat of reaction of the oxidation of the mercaptan or dialkyl sulfide is preferably removed to the reaction mixture by a condenser in the exhaust gas stream with condensate recirculation.
• step (a) is carried out in a reactor cascade with two reactors with a high degree of backmixing, the alkyl mercaptan or dialkyl disulfide or dialkyl polysulfide used is largely oxidized in the first reactor, essentially the corresponding alkanesulfonic acid and, in small amounts, incomplete oxidation products in addition to excess nitric acid and minor Amounts of sulfuric acid arise.
• the yield of alkanesulfonic acid in the mixture at this stage of the reaction is usually already over 80%, preferably over 90%, based on the amount of mercaptan and / or dialkyl disulfide and / or dialkyl polysulfide used.
• the oxidation reaction is completed in the second reactor, as a result of which the yield of alkanesulfonic acid is usually increased to over 90%, preferably over 93%.
• the excess nitric acid contained in the discharge from reaction step (a) (with) can be separated off by distillation by simple distillation in a manner known per se and into the oxidation of mercaptans and / or dialkyl disulfides and / or dialkyl polysulfides (step (a)) or in the regeneration of the nitrogen oxides with oxygen to nitric acid (step (b)).
• the other by-products formed in the reaction discharge from step (a) can also be separated from one another by distillation, the products of an incomplete oxidation preferably being returned to the oxidation (step (a)).
• nitric acid is kept almost completely in the system, the only losses occur due to a very low formation of nitrous oxide and an incomplete absorption in step (b).
• the absorption losses are, however, only small according to the current status of modern nitric acid plants.
• the second reactor is followed by a water separation column operated as a stripping column.
• a water separation column operated as a stripping column. This separates water and nitric acid as the top product; a colorless 98% alkanesulfonic acid with about 1% by weight of water and about 1% by weight of sulfuric acid is typically obtained as the bottom product.
• Nitric acid is only contained in traces of ⁇ 0.2% by weight.
• the column is generally operated at 20 to 1000 mbar, preferably at 50 to 300 mbar and at bottom temperatures of generally 130 to 240 ° C., preferably from 150 to 200 ° C.
• NO x essentially means NO, NO 2 , N 2 O 3 , N 2 O 4 and NO 5 .
• the concentration of the nitric acid used in the process according to the invention is generally 20 to 100% by weight, preferably 40 to 70% by weight, particularly preferably 50 to 70% by weight.
• Step (b) is preferably carried out isothermally at temperatures from 0 ° C. to 60 ° C., particularly preferably from 0 ° C. to 30 ° C.
• the absolute pressures are preferably between 0.5 and 20 bar, particularly preferably between 3 and 12 bar.
• the regeneration of the nitrogen oxides in step (b) also acts as waste gas scrubbing for the sulfur compounds formed as by-products in step (a), so that the process waste gas is free from malodorous mercaptans or dialkyl disulfides or dialkyl polysulfides and its composition roughly corresponds to that of conventional nitric acid plants.
• the exhaust gas can thus be released into the environment without additional aftertreatment.
• the oxygen used for regeneration is generally atmospheric oxygen.
• An absorption column is generally used as the reaction apparatus. It is preferably a cooled absorption column which corresponds to the known columns for the production of nitric acid from nitrogen oxides. This can be, for example, boiling, valve, bell, tunnel-bottom columns or columns with packed or ordered ones Trade packs.
• the cooling can take place both in the column and in external heat exchangers.
• the Abso ⁇ tionskolonne is generally operated at 0 to 60 ° C, preferably at 0 to 30 ° C, preferably isothermal.
• Fresh water is fed in at the top of the column, preferably demineralized water, where a lean air largely freed of nitrogen oxides escapes, i.e. air depleted in oxygen.
• the nitric acid present in step (a) in the reaction discharge after separation from the reaction discharge in step (a) or step (b) is preferably recycled, and the products likewise incomplete oxidation after separation in step (a) returned.
• the already very pure alkanesulfonic acid obtained in the process according to the invention can be purified in a downstream vacuum distillation column which generally works at head pressures of 0.1 to 20 mbar, preferably 2 to 10 mbar. Traces of impurities are separated off in the top or bottom of the column.
• the actual alkanesulfonic acid is usually obtained in a side draw.
• the alkanesulfonic acid obtained is colorless and generally has a purity of> 99%, preferably of> 99.5% with a sulfuric acid content of ⁇ 50 ppm. Methanesulfonic acid obtained in this way is e.g. suitable for use in galvanic baths.
• methanesulfonic acid is very particularly preferably prepared by oxidation of dimethyl disulfide.
• the methanesulfonic acid obtained after purification (vacuum distillation) has in generally a purity of> 99% and is colorless.
• the sulfuric acid levels are generally less than 50 ppm.
• Such a methanesulfonic acid is particularly suitable for use in galvanic baths.
• FIG. 1 the method according to the invention is shown schematically in FIG. 1.
• the reactor A is continuously stirred over 1 with pure
• the liquid stream 9 leaving reactor A continuously consists of approx. 32% methanesulfonic acid, 11% nitric acid, 0.6% methanethiosulfonic acid S-methyl ester and 56% water and is fed to reactor B.
• the temperature in reactor B is 130 ° C.
• the residence time in reactor B calculated as the quotient of the liquid volume in reactor B, divided by the liquid stream 13 continuously leaving reactor B, is approximately 2.2 hours.
• the liquid stream 13 leaving the reactor B continuously consists of approx. 55% methanesulfonic acid, 10% nitric acid, ⁇ 0.2% methanethiosulfonic acid S-methyl ester and 35% water and is fed to the vacuum rectification column G just below the top of the column.
• the crude yield of methanesulfonic acid in stream 9 is> 95%.
• the vacuum rectification column G works at 95 to 100 mbar head pressure (absolute) and 180 to 190 ° C. bottom temperature.
• the bottom discharge 15 leaving the vacuum rectification column G consists of approx. 98% methanesulfonic acid, approx. 1% water and approx. 1% sulfuric acid and is fed to the vacuum rectification column J.
• the vacuum rectification column J operates at a top pressure of about 5 to 10 mbar (absolute) and a bottom temperature of about 180 to 190 ° C.
• the side draw stream 7 leaving the vacuum rectification column J consists of> 99% methanesulfonic acid with a sulfuric acid content of ⁇ 50 ppm.
• the total yield of methanesulfonic acid after distillation is> 90%.
• the top discharge stream 6 leaving the vacuum rectification column J consists of water, methanesulfonic acid, methanesulfonic acid methyl ester and other low boilers.
• the bottom discharge stream 8 leaving the vacuum rectification column J consists of sulfuric acid, methanesulfonic acid and other high boilers.
• the tray column for nitric acid regeneration E works at normal pressure and at temperatures of 20 to 45 ° C.
• the bottom column for nitric acid regeneration E is supplied with 4 deionized water via the feed.
• the air fed to the bottom column for regeneration of nitric acid E via stream 3 for reoxidation of the nitrogen oxides leaves the column at the top exit 5 with a reduced oxygen content (7 to 13% by volume).
• the NO x -containing exhaust gas stream 10 formed in the reactor A and freed from condensable components in the condenser C contains NO and NO 2 and is fed to the bottom column for the regeneration of nitric acid E.
• the NO x -containing flue gas stream 11 formed in the reactor B and freed from condensable components in the condenser D contains NO and NO 2 and is fed to the bottom column for the regeneration of nitric acid E.
• the condensate 12 consists of approx. 7% nitric acid and is fed to the tray column for nitric acid regeneration E on a tray with a similar concentration of nitric acid.
• the condensate 14 consists of approx. 23% nitric acid and is fed to the tray column for nitric acid regeneration E on a tray with a similar concentration of nitric acid.
• the bottom effluent from the bottom column to the nitric acid regeneration E to the nitric acid buffer container F consists of approximately 45 to 50% nitric acid and is fed to the reactor A.
• Nitric acid losses are replaced by replenishing the required amounts of 50 to 65% nitric acid via stream 2 into the nitric acid buffer container F.

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• 1998
  • 1998-11-25 DE DE19854428A patent/DE19854428A1/de not_active Withdrawn
• 1999
  • 1999-11-22 KR KR1020017006113A patent/KR100599637B1/ko not_active Expired - Lifetime
  • 1999-11-22 US US09/831,362 patent/US6531629B1/en not_active Expired - Lifetime
  • 1999-11-22 ES ES99962150T patent/ES2200582T3/es not_active Expired - Lifetime
  • 1999-11-22 CN CNB998136883A patent/CN1163479C/zh not_active Expired - Lifetime
  • 1999-11-22 BR BRPI9915651-2A patent/BR9915651B1/pt not_active IP Right Cessation
  • 1999-11-22 JP JP2000583855A patent/JP4294874B2/ja not_active Expired - Fee Related
  • 1999-11-22 AU AU18593/00A patent/AU765481B2/en not_active Ceased
  • 1999-11-22 WO PCT/EP1999/008994 patent/WO2000031027A1/de active IP Right Grant
  • 1999-11-22 SK SK715-2001A patent/SK7152001A3/sk unknown
  • 1999-11-22 AT AT99962150T patent/ATE240938T1/de active
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  • 1999-11-22 UA UA2001064423A patent/UA66896C2/uk unknown
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• 2001
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